The present invention relates to a portable device including a cellular phone, and more particularly, it relates to a mounting structure of a small dc motor built in the portable device.
A portable device, e.g., a cellular phone, integrating a small dc motor (hereinafter referred to as a motor) sometimes needs countermeasures against electrical noises produced by the motor. The following countermeasures are commonly available in the trade:
(a) Place the motor distant from the components vulnerable to the noises;
(b) Shield the components vulnerable to the noises by disposing a shielding member made of metal between the components and the motor;
(c) Rigidly mount the motor to a metallic component, e.g., a chassis of the device, with metallic parts such as screws, thereby shorting the motor to the ground on the device; and
(d) Short electrically one of pair terminals of the motor to the motor frame by, e.g., soldering.
Countermeasure (d) is disclosed in the Japanese Patent Application Non-Examined Publication No. H10-84649. This disclosure refers to a motorxe2x80x94for generating vibrationsxe2x80x94mounted to a cellular phone. FIG. 5 shows a structure of this motor, and FIG. 6 shows a lateral view of a holder of the motor. In FIG. 5, first terminal 101 coupled to a first brush is conductive to motor frame 102, and second terminal 103 coupled to a second brush is conductive to conductive plate 104 on an end face of the motor. Frame 102 is sandwiched by a pair of elastic holding slips 111 of the motor holder shown in FIG. 6, and both the elements are conductive and contact to each other. Conductive plate 104 is urged by elastic conductor 112 shown in FIG. 6, and both the elements are conductive and contact to each other. In the conventional motor shown in FIG. 5, one of pair terminals of the motor is electrically conductive to frame 102.
This structure allows the motor to be attachable with more ease than coupling with a lead-wire, and to obtain desirable electrical conductivity. Recently, when people go out, they always carry the cellular phone. Thus the cellular phone often encounters a large shock. Further, the motor, per se, is a vibration generator, and the conductive contact section of the motor holder repeatedly slides with respect to the frame due to self-vibrations. Then the conductive contact section produces high polymers and results in faulty conduction. This slide can be prevented by strengthening the elastic holding slips of the motor holder; however, the motor is attached not so easy as expected because of the strengthened elastic holding slips.
The motor is wrapped in rubber holder, and then mounted to a device. This structure has better vibration-resistant and shock-resistant characteristics than the structure discussed previously. In this motor, a terminal coupled to a first brush can be conductive to the motor frame; however this coupling cannot be carried out due to the structure of the motor, or this structure causes uneasiness in coupling reliability. Someone needs a thicker grounding conductive line than that of this structure, or another one wants to shorten the grounding conductive line by connecting the motor frame direct to the device. Thus a grounding coupling structure which meets those requests is desired, and yet, the structure is desirably highly reliable and reduces noises substantially.
The present invention addresses the problems discussed above and aims to provide an excellent device free from radio interference.
The device of the present invention comprises the following elements:
(a) a motor including a frame of which surface is conductive;
(b) a grounding terminal disposing at a place facing the frame; and
(c) an elastic member made of conductive resin and disposed between the frame and the grounding terminal.
This structure allows the conductive frame and the confronting grounding terminal to be conductive to each other via the elastic member made of conductive resin. Thus when an impact is applied to the device, the device elastically follows and damps the impact. Further, the device and the frame can be conductive through the shortest conductive line with low impedance.
Another device of the present invention comprises the following elements:
(a) a motor including a frame of which surface is conductive and motor terminals shaping in leaf springs;
(b) feeding terminals for powering the motor and disposed at a place facing the motor terminals;
(c) a grounding terminal disposed at a place facing the frame;
(d) a first elastic member made of insulating resin and disposed such that the member urges the motor terminals to the feeding terminals, so that the motor terminals are conductive to the feeding terminals; and
(e) a second elastic member made of conductive resin and disposed between the frame and the grounding terminal.
Still another device of the present invention comprises the following elements:
(a) a motor including a frame of which surface is conductive, a first motor terminal and a second motor terminal, both the terminals shaping in leaf springs;
(b) a first feeding terminal for powering the motor and disposed at a place facing the first motor terminal;
(c) a second feeding terminal for powering the motor and disposed at a place facing the second motor terminal;
(d) a first elastic member made of insulating resin and disposed such that the member urges the first motor terminal to the first feeding terminal, so that the first motor terminal is conductive to the first feeding terminal; and
(e) a second elastic member made of conductive resin and disposed between the frame and the second feeding terminal, and disposed such that the member urges the second motor terminal to the second feeding terminal, so that the second motor terminal is conductive to the second feeding terminal.
These structures allow the motor to be mounted to the device with ease thanks to employing leaf-spring type motor terminals. The terminals are urged to the feeding terminals of the device by the elastic members, so that highly reliable coupling between the terminals and the feeding terminals can be obtained. The motor frame and the device can be conductive through the shortest conductive line with low impedance. As a result, a reliable conductive structure having substantial noise reduction effect is achievable, and thus the device free from radio interference can be provided.
A motor of the present invention is suitable to be mounted to the device discussed above, and the motor has the following structure:
the motor including a frame of which surface is conductive, where the frame is conductive to a grounding terminal of the device via an elastic member made of conductive resin.
Another motor of the present invention comprises the following elements:
a frame of which surface is conductive; and
motor terminals shaping in leaf springs,
where the motor terminals are urged to feeding terminals on the device side by a first elastic member made of insulating resin, and the frame becomes conductive to a grounding terminal of the device via a second elastic member made of conductive resin.
Still another motor of the present invention comprises the following elements:
a frame of which surface is conductive; and
a first motor terminal and a second motor terminal, both terminals shaping in leaf springs,
where the first motor terminal is urged to a first feeding terminal of the device by a first elastic member made of insulating resin,
the second motor terminal is urged to a second feeding terminal of the device by a second elastic member made of conductive resin, and
the frame becomes conductive to the second motor terminal via the second elastic member.
These motors structured above are mounted to the device, thereby providing advantages specific to the present invention.